Sequence identity in an early chorion multigene family is the result of localized gene conversion.
Sequence identity in an early chorion multigene family is the result of localized gene conversion.
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早期绒毛膜多基因家族中的序列同一性是局部基因转换的结果。
DOI：
10.1093/genetics/128.3.595
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发表时间：
1991
期刊：
影响因子：
3.3
通讯作者：
Eickbush,TH
中科院分区：
文献类型：
--
作者：
Hibner,BL;Burke,WD;Eickbush,TH
蚕蛾(Bombyx Mori)绒毛膜(蛋壳)的多基因家族紧密连接在一条染色体上。我们在这里报告了两个片段的分离和鉴定，总共102kb的基因组DNA，包含在绒毛形成早期表达的基因。这些早期基因大多可分为era和erb两个多基因家族，它们被组织成5个差异转录的era/erb基因对。ERA基因主要编码区的核苷酸序列同源性为96%，而ERb主要编码区的核苷酸序列同源性仅为63%。编码蛋白的选择压力不能解释ERA和ERB基因家族在序列保守水平上的差异，因为当只考虑四个冗余密码子位置时，Era基因内的差异为8%，而ERb基因内的差异(校正了同一位置的多个替换)为110%。Era主要外显子的高度序列同源性可以通过类似于定位于Era基因主要外显子的基因转换的序列交换事件来解释。这些基因转换与编码成对甘氨酸残基的核苷酸序列GGXGGX的簇状拷贝的存在相关。该序列与家蚕高半胱氨酸(HC)绒毛膜基因的编码区和非编码区的基因转换梯度相关。我们认为，这些基因家族中转换区范围的差异反映了这些重组事件随着时间的推移而定位于主要外显子的蛋白质编码区的趋势。
The multigene families that encode the chorion (eggshell) of the silk moth, Bombyx mori, are closely linked on one chromosome. We report here the isolation and characterization of two segments, totaling 102 kb of genomic DNA, containing the genes expressed during the early period of choriogenesis. Most of these early genes can be divided into two multigene families, ErA and ErB, organized into five divergently transcribed ErA/ErB gene pairs. Nucleotide sequence identity in the major coding regions of the ErA genes was 96%, while nucleotide sequence identity for the ErB major coding regions was only 63%. Selection pressure on the encoded proteins cannot explain this difference in the level of sequence conservation between the ErA and ErB gene families, since when only fourfold redundant codon positions are considered, the divergence within the ErA genes is 8%, while the divergence within the ErB genes (corrected for multiple substitutions at the same site) is 110%. The high sequence identity of the ErA major exons can be explained by sequence exchange events similar to gene conversion localized to the major exon of the ErA genes. These gene conversions are correlated with the presence of clustered copies of the nucleotide sequence GGXGGX, encoding paired glycine residues. This sequence has previously been correlated with gradients of gene conversion that extend throughout the coding and noncoding regions of the High-cysteine (Hc) chorion genes of B. mori. We suggest that the difference in the extent of the conversion tracts in these gene families reflects a tendency for these recombination events to become localized over time to the protein encoding regions of the major exons.